The microcontroller is part of a circuit board which contains a large ground plane. This in itself will protect the IC. There is also regulation and filter circuitry onboard which will also offer some level of protection.

If this is some sort of mission critical system, where failure would be very expensive and/or impossible to fix, then ESD protocols should be followed.

The vast majority of Arduinos will live in an ESD-unsafe (maybe even ESD-hostile) environment for the rest of their lives once they're removed from the box. This does not appear to be a problem to date.

How do you think ESD materials work? They are simply a conductive material on which charged electrons repulsed by all having the same charge, move away from each other which forces them onto the outside of the bag and away from the component.

If you take a microcontroller, it is not conductive, apart from the pins. This means that the ESD builds up on one or more of the pins creating a potential difference across the IC of anywhere upwards of 10kV. This can damage the IC.

If however you take an IC connected to a board with a ground plane. Where does the ESD go? Well, all the electrons can happily transfer to the ground plane which is nicely conductive and move away from each other, and critically away from the IC. This means there is no buildup of potential across the IC pins.

As a side note while that board is nicely inside its cardboard box, where does an electrostatic discharge come from? Last time I checked the box isn't particularly conductive, so it is unlikely that a discharge will jump to the box, and if it does, it will built up on the outer surface - just like an ESD bag.

Electronic Technician, Electronic Engineering Technician
I love to build things. Test equipment, replica and original sci fi props and costume pieces, and whatever else I feel like at the time. I have an Ultimaker and a 3D engraver.

I think a lot of newbies are discouraged by damaged devices, thinking that they are doing something wrong. More and more distributors are shipping with partial or no ESD safety precautions.

Sure, modern ICs have more built-in ESD protection, but why stress it? There is a misunderstanding about how static charges build up, that it requires conductors. It does not. Usually at least one side is an insulator, or both. At one of my jobs, we took all kinds of ESD precautions, but then big nylon web belts were loaded into grey plastic buckets. Sometimes a huge charge would build up inside the bucket, causing the outside metal carrier to be charged by induction. You'd get a rather hefty shock from grabbing the metal, then reach inside and really get hit.

It generally takes a few thousand volts charge for you to feel, hear, and see it. But it may take as little as 20V to blow a MOSFET or BJT.

Electronic Technician, Electronic Engineering Technician
I love to build things. Test equipment, replica and original sci fi props and costume pieces, and whatever else I feel like at the time. I have an Ultimaker and a 3D engraver.

Some of the cleaning staff here thinks that they can't mop our grounding floor mats "because they're wired to electricity". Well, if it stops them from mopping them, we leave well enough alone. It isn't their job to know.